This invention relates to the vaporization and spraying of materials and, more particularly, to such spraying induced by laser heating.
In many modern materials systems, it is necessary to add layers of a material to an existing substrate. In some circumstances, a coating of a hard, wear resistant material is overlaid onto a strong, ductile material. The resulting composite provides a structural component that has good mechanical properties such as strength, ductility, and fracture toughness, and also has a surface that does not wear rapidly in environments that are erosive and/or corrosive. In another application, a part can be repaired by adding to the substrate new material of the same (or a different) composition as the substrate, gradually building up a thickness of the added material to replace that which may have been lost during service. Many other applications of coating are in widespread use, because of the versatility afforded in designing custom materials systems.
The layers of the material may be added to the substrate in many different ways, depending upon the substrate, the added material, and the performance required. The added material may be provided in a bulk form and laminated, bonded, or affixed to the substrate. Alternatively, the material to be added can be provided in a form different from its final configuration and applied to the substrate atomically, often in either the molten or vaporous state. In many instances, the latter type of approach is preferred to produce an excellent bond of the added material to the substrate and to produce a highly controllable final product.
In one widely practiced approach, a plasma is formed with an electric arc. Metal powder in a gas stream is directed through the plasma, causing the metal to melt and form metal droplets. The molten metal is then sprayed against a substrate to solidify as a coating or built-up layer. Plasma spraying and other similar techniques are not operable for some metals, such as, for example, titanium alloys sprayed in an atmospheric environment. Additionally, the geometry of the plasma spray apparatus is not suitable for applying the sprayed metal to some forms of substrates, such as the interior of bores.
Therefore, there is a need for a new approach to depositing materials on substrates, that permits deposition of the material into constricted or inaccessible locations. The present invention fulfills this need, and further provides related advantages.